For filing of these sheets, binders now used are of the suspended type or of type to be filed on end on a shelf and comprising along the folding line separating their bottom and back, two means for fastening of the sheets which are solid with the bottom and able to go through two perforations corresponding to one another along the two opposite sides of the stacked sheets; these means are generally flexible rods bent on a removable rail applied against the upper sheet between the two perforations corresponding to one another along the two opposite sides of the stacked sheets; these means are generally flexible rods bent on a removable rail applied against the upper sheet between the two perforations and having slides for wedging the free ends of the two flexible rods.
Although in some cases, mobility has been provided for one of the means along the edge of the binder, to allow it to adapt to the width of the sheets and consequently to the distance separating the two rows of perforations, the binders do not allow folding of the sheets on themselves without risk of tearing them, which requires filing means suited to the very special dimensions of the sheets, dimensions which always exceed the standard dimensions of current documents. Further, the fastening means do not allow easy looking at the part located at the top of the sheets.